The present patent relates to verification that an audio alarm has been sounded by a speaker upon activation of the alarm from a controller or other device. The verification particularly relates to patients using medical machines, such as dialysis machines, and even more particularly extracorporeal blood machines, such as hemodialysis machines, apheresis machines, and heart-lung operation machines.
Modern medical machines perform a variety of life-sustaining and life-preserving tasks, from peritoneal dialysis and hemodialyis, to plasmapheresis, and even performing blood circulation and oxygenation that allows surgeons to perform medical procedures during a heart-bypass operation. Of course, machines are not perfect and conditions can arise during their use that threatens the completion or the quality of the procedure. For example, if a peristaltic pump is used to convey blood within tubing, the pump head could break, the motor could stall, and the tubing could develop leaks. Sensors on the instrument would detect these conditions in at least one way, such as a loss of blood pressure or a drop in motor current.
If one of these failures occurred, for example, during a coronary artery bypass procedure, an alert operator on the medical team would immediately detect the condition and would take action to substitute a back-up machine or otherwise correct the situation. Other procedures, however, may have only a single operator, such as a caregiver, or may have only the patient present while the procedure is performed. An example is plasmapheresis. Plasmapheresis typically takes place at a medical center, with a head nurse or other professional to supervise one or more patients undergoing the procedure. If a machine failure occurs, or an unsafe condition develops, the plasmapheresis machine may flash a warning light or a warning on a video screen, or more likely, sound an audio alarm, such as a buzzer. The audio alarm alerts the patient or a nurse or other caregiver, or both, that attention is needed. If for any reason the audio alarm does not sound, the patient or nurse may notice the visual alarm or alert and is then motivated to correct the situation.
The audio alarm may not sound if there is an alarm fault, such as a connectivity fault, in the chain between the machine fault or failure and the audio speaker that is intended to sound an alarm or alert as a result of the machine fault or failure, or other condition for which an alarm is desired. For example, an electrical wire may become disconnected from a speaker connection, or the wire may break, thus preventing an audio signal from reaching the speaker. Other electrical or physical problems could also result in a failure of the speaker to emit audible sound, such as failure of a relay within the control system, disconnection of power to an audio amplifier, or disconnection of a ground from the circuit.
If an audio alarm fails to sound through the speaker, as noted above, corrective action is needed but personnel may not be alerted to the need. There are several ways to detect the failure of the sound. For example, the machine of which the speaker is a part may be equipped with a local microphone for detection of sound from the speaker. If the machine control system attempts to sound an audio alarm, but the alarm is not detected by the microphone, the failure to detect is interpreted as a speaker or other system failure and corrective action can be taken. Examples are depicted in U.S. Pat. Nos. 5,736,927 and 6,094,134. However, this method requires a separate microphone near the speaker, an amplifier and tuner for the microphone, as well as tuning of the microphone, and additional programming to perform the analysis and then to follow up. In addition, this system would be subject to interference from nearby noise, possibly including interfering noise that would mask the speaker output from detection by the microphone.
What is needed is a way to ensure that when a medical device or machine sounds an alert or an alarm, that the intended speaker has actually sounded the alert or alarm. If the alarm has not been sounded, the medical device or machine is then programmed to take additional steps, such as sending a visual alert or alarm, or placing the machine in a safe mode.